Capacitive sensor devices are often implemented in display application such as touch screens. Different sensing technology using mutual and self capacitive sensing are used to detect a touch position. Further developments provide for non-touching input systems that generate an alternating electric near field and measure distortions of such a field with for example, four electrodes arranged in a frame around a display to determine three-dimensional position data of objects entering the field. Such a system is also known as the GestIC® system and has been developed by the assignee of the present application and a general description is for example disclosed in application note “MGC3130—Sabrewing Single-Zone Evaluation Kit User's Guide”, published 2013 by Microchip Technology Inc. which is hereby incorporated by reference.
FIG. 1 shows a sensor electrode arrangement 100 as disclosed in FIG. 3-2 of the above mentioned publication. A printed circuit board (PCB) 110 comprises on the top side a plurality of primary receiving electrodes A, B, C, and D arranged in a frame fashion and a center receiving electrode 130. The center electrode may have a hashed structure as shown in FIG. 3-2 of the above mentioned publication. These electrodes are connected with a controller 120 through a respective connector on the PCB or the controller may be arranged on the PCB, whether on the top or the back side. To this end, the PCB can be a dual or multi-layered board and a back side may be used in its entirety as a ground electrode or as a transmission electrode. If it used as a ground electrode with respect to a multi-layer PCB, then any intermittent layer may be used as a transmission electrode wherein the entire layer or parts of it (similar in size as electrode 130) may serve as the transmission electrode. The ground and/or transmission electrode are connected with a controller 120 as indicated with the dashed connection lines. The controller generates a drive signal for the transmission electrode, for example, an alternating square wave- or sinusoidal-signal having a frequency of about 100 kHz. The controller receives signals from the top electrodes A, B, C, D, and 130 and processes these signals to detect gestures performed by an object, for example, a hand or finger, in a detection space above the PCB. Respective commands can then be sent to a host system 140.